Try one of those Mr. Clean Magic Eraser with Dawn. The hood over my stove was gooey, gummy and disgusting. This thing cleaned it with very little effort. I swear, these Magic Erasers are incredible. I don't know how they work but they do. I would try this.

Gun threads are very fine. Becareful what you use to remove the cooking oil as it has entered the screw ports. You need a deep penetrating petro chem just soak it in Kerosene for a week it will free the screws. Kero has been used to clean badly rusted or coated firearms for years.